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Nov 2013 p13 q11
1164
The diagram shows the curve \(y = \sqrt{x^4 + 4x + 4}\).
(i) Find the equation of the tangent to the curve at the point \((0, 2)\).
(ii) Show that the \(x\)-coordinates of the points of intersection of the line \(y = x + 2\) and the curve are given by the equation \((x + 2)^2 = x^4 + 4x + 4\). Hence find these \(x\)-coordinates.
Solution
(i) To find the equation of the tangent, we first differentiate the curve \(y = \sqrt{x^4 + 4x + 4}\).
The derivative is \(\frac{dy}{dx} = \left[ \frac{1}{2} (x^4 + 4x + 4)^{-\frac{1}{2}} \right] \times [4x^3 + 4]\).